Sealant for liquid crystal and liquid-crystal display cell made with the same

ABSTRACT

An objective of this application is to provide a sealant for liquid crystals witch is extremely less apt to contaminate liquid crystals and has high adhesion strength. This application discloses a sealant for liquid crystals comprising as essential ingredients (a) a radiation-curable resin represented by the general formula (1): 
                         
wherein R 1  represents a hydrogen atom or a methyl group, R 2  represents a hydrogen atom, a halogen atom, a hydroxyl group, a linear, branch or cyclic monovalent alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms, m represents an integer of 1 to 4, and may be the same or different, R 3  represents a hydrogen atom or a methyl group, and the number n of the repeating units is a positive number in the range of 0 to 20; (b) a photopolymerization initiator; and (c) an inorganic filler having an average particle diameter of 3 μm or less.

This application is a 371 of PCT/JP04/06646 filed May 18, 2004.

TECHNICAL FIELD

The present invention relates to a sealant for liquid crystals and aliquid crystal display cell made with the same. More specifically, thepresent invention relates to a sealant for liquid crystals which can beused for the production of a liquid crystal display cell by droppingliquid crystals inside the photo-and-heat-curing type sealant for liquidcrystals formed on a substrate, attaching another substrate thereto andcuring this sealant for liquid crystals thereby sealing the liquidcrystals, and a liquid crystal display cell made with the same.

BACKGROUND ART

With the increase in the size of a liquid crystal display cell in recentyears, so-called liquid crystal dropping method has been proposed as aprocess for producing a liquid crystal display cell higher in massproductivity (see Japanese Patent Application Laid-open Nos. 63-179323and 10-239694). Specifically, it is a process for producing a liquidcrystal display cell comprising dropping liquid crystals inside asealant for liquid crystals formed on a substrate and then attachinganother substrate thereto thereby sealing the liquid crystals.

However, the liquid crystal dropping method has a problem that a sealantfor liquid crystals in an uncured state contacts the liquid crystal atfirst and at that time the ingredients of the sealant for liquidcrystals dissolve in the liquid crystals, which causes defect ofreducing the specific resistance of the liquid crystal and therefore themethod has not been fully spread as a mass-production method of liquidcrystal display cell.

There have been contemplated three methods in the liquid crystaldropping method, i.e., a heat-curing method, a photo-curing method and aphoto-and-heat-curing method as a method for curing a sealant for liquidcrystals after attaching the substrates together. The heat-curing methodhas problems that the liquid crystals expanded by heating leak out ofthe sealant for liquid crystals which is lowered in viscosity in themiddle of curing and that ingredients of the sealant for liquid crystalswhich is lowered in viscosity dissolve in the liquid crystals, and theseproblems are difficult to solve. Therefore, the heat-curing method isnot yet put in practical use.

On the other hand, the sealant for liquid crystals used for thephoto-curing method includes two types, cationic polymerization type andradical polymerization type depending on the type of photopolymerizationinitiator. As for the cationic polymerization type sealant for liquidcrystals, there is a problem that ions are generated at the time ofphoto-curing and when it is used in the liquid crystal dropping method,the ionic ingredients elute in the liquid crystals in contact therewithand decreases the specific resistance of the liquid crystals. Inaddition, since the curing contraction of the radical polymerizationtype sealant for liquid crystals at the time of photo-curing is large,there is a problem that adhesion strength is not sufficient.Furthermore, as a problem common in the photo-curing methods of both thecationic polymerization type and the radical polymerization type, thereis a problem that shaded parts which are not irradiated with light areresulted in the sealant for liquid crystals due to metal wiring of thearray substrate of liquid crystal display cell or black matrix of colorfilter substrate and such shaded parts remain uncured.

In this way, various problems are involved in the heat-curing method andthe photo-curing method, and actually photo-and-heat-curing method isconsidered to be the most practical method. The photo-and-heat-curingmethod is characterized in that after the sealant for liquid crystalsplaced between the substrates is irradiated with light to performprimary curing, it is heated to perform secondary curing. As propertiesrequired of the sealant for liquid crystals used for thephoto-and-heat-curing method, it is important that the sealant forliquid crystals does not contaminate the liquid crystals in each stepbefore and after the light irradiation and before and after the heatcuring. Particularly needed are measures to deal with the problem byshaded parts described above, i.e., measures to deal with the elution ofthe ingredients of the sealant into the liquid crystals at the time ofheat-curing from the parts which are not photo-cured. As a solutiontherefor, there may be considered (i) an approach in which rapid curingis performed at a low temperature before the ingredients of the sealantelute, or (ii) an approach to constitute the sealant with ingredientswhich hardly elute into the liquid crystal composition, and so on.Naturally, however, rapid curing at a low temperature concurrently meansthat the pot life at the time of use is deteriorated, and poses apractically large problem. Therefore, in order to attain a sealant forliquid crystals having a long pot life and achieving low contaminationof liquid crystal, it is necessary to constitute the sealant withingredients which hardly elute into the liquid crystal composition.However, since epoxy resins generally known well, for example, bisphenolA epoxy resin and bisphenol F epoxy resin have good compatibility withliquid crystal, it is hard to say that they are suitable as ingredientsof a sealant composition from a viewpoint of contaminating properties.

Japanese Patent Application Laid-open No.2001-133794 proposes to use apartially (meta)acrylated bisphenol A type epoxy resin described inJapanese Patent Application Laid-open No.5-295087 as the main resiningredient for a sealant for liquid crystals for dropping method (seeJapanese Patent Application Laid-open Nos. 2001-133794 and No.5-295087). However, the solubility to the liquid crystal is reduced butunsatisfactorily by (meta)acrylation, and it is also difficult to solvethe problem that the unreacted and remained epoxy resin materialcontaminates the liquid crystal.

As explained above, photo-and-heat-curing type sealant for liquidcrystals for a liquid crystal dropping method conventionally proposedare not satisfactory in all of the properties such as liquid crystalcontaminating properties, adhesion strength, usable life at roomtemperature, and low-temperature curing properties.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As explained above, partially acrylated substance of bisphenol typeepoxy resin is mainly used at present for a sealant for liquid crystalsdropping method. However, the partially acrylated substance of bisphenoltype epoxy resin has a problem that it is likely to elute when incontact with a liquid crystal or when heated in contact with a liquidcrystal, which causes poor orientation of the liquid crystal and displayirregularities, and reduces reliability of a panel.

On the other hand, totally acrylated substance of bisphenol type epoxyresin is relatively hard to elute into the liquid crystal, but it is notnecessarily enough. Moreover, since the viscosity was high, there wasalso a problem that the other ingredients which could be used weregreatly limited when it was used as a sealant for liquid crystalscomposition.

The present invention relates to a sealant for liquid crystals which canbe used for liquid crystal dropping method for the production of aliquid crystal display cell by dropping liquid crystals inside thesealant for liquid crystals formed on a substrate, attaching anothersubstrate thereto, irradiating the liquid crystal sealing parts followedby heat curing and the present invention proposes a sealant for liquidcrystals which is extremely less apt to contaminate the liquid crystalthrough the process and further the ingredients of which scarcely eluteinto the liquid crystal even at shaded parts and which are excellent inapplication workability onto the substrate, attaching properties,adhesion strength and low-temperature curability.

Means to Solve the Problems

The present inventors have conducted intensive studies for solving theabove mentioned problems and consequently completed the presentinvention. The radiation curable resin of the present invention has verylow compatibility with the liquid crystal composition, and the sealantfor liquid crystals made with the same is extremely less apt tocontaminate the liquid crystals. Moreover, since the radiation curableresin used in the present invention has low viscosity, it imposes smallrestrictions on the other ingredients which can be used when the resinis made into a sealant for liquid crystals composition and enables touse together a resin having a higher viscosity and enables to be filledwith more filler.

That is, the present invention relates to the following:

-   (1) A sealant for liquid crystals comprising as essential    ingredients (a) a radiation curable resin represented by the general    formula (1):

wherein R¹ represents a hydrogen atom or a methyl group, R² represents ahydrogen atom, a halogen atom, a hydroxyl group, a linear, branch orcyclic monovalent alkyl group having 1 to 10 carbon atoms, or an alkoxygroup having 1 to 10 carbon atoms, m represents an integer of 1 to 4,and may be the same or different, R³ represents a hydrogen atom or amethyl group, and the number n of the repeating units is a positivenumber in the range of 0 to 20; (b) a photopolymerization initiator; and(c) an inorganic filler having an average particle diameter of 3 μm orless,

-   (2) The sealant for liquid crystals according to (1), wherein the    radiation curable resin (a) is a radiation curable resin represented    by the general formula (2):

wherein the number p of the repeating units is a positive number in therange of 0 to 20,

-   (3) The sealant for liquid crystals according to (1) or (2), wherein    the radiation curable resin (a) has a content of 30% by weight to    80% by weight based on the total sealant for liquid crystals,-   (4) The sealant for liquid crystals according to any one of (1) to    (3), wherein the radiation curable resin (a) has a viscosity of 30    to 500 Pa·S,-   (5) The sealant for liquid crystals according to any one of (1) to    (4), wherein the photopolymerization initiator (b) is a radical type    photopolymerization initiator,-   (6) The sealant for liquid crystals according to (5), wherein the    radical type photopolymerization initiator (b) is a carbazole    initiator,-   (7) The sealant for liquid crystals according to any one of (1) to    (6), further comprising (d) an epoxy resin and (e) a heat-curing    agent,-   (8) The sealant for liquid crystals according to (7), wherein the    epoxy resin (d) is an epoxy resin which does not elute into the    liquid crystals in an amount of 0.5% by weight or more based on the    liquid crystals when the epoxy resin is brought directly into    contact with the liquid crystals whose amount is 10 times of the    epoxy resin and is allowed to stand at 120° C. for 1 hour,-   (9) The sealant for liquid crystals according to (7) or (8), wherein    the heat-curing agent (e) is a dihydrazide,-   (10) The sealant for liquid crystals according to (9), wherein the    dihydrazide is a dihydrazide having a skeleton of isophthalic    dihydrazide and/or valine hydantoin,-   (11) The sealant for liquid crystals according to (7) or (8),    wherein the heat-curing agent (e) is a polyhydric phenol,-   (12) The sealant for liquid crystals according to any one of (1) to    (11 ) further comprising (f) a silane coupling agent,-   (13) The sealant for liquid crystals according to (12), wherein the    silane coupling agent is a silane coupling agent having an amino    group,-   (14) A liquid crystal display cell which is sealed with a cured    product of a sealant for liquid crystals according to any one of (1)    to (13), and-   (15) A process for producing a liquid crystal display cell    comprising dropping liquid crystals inside a sealant for liquid    crystals according to any one of (1) to (13) formed on a substrate    and attaching another substrate thereto.

Effects of the Invention

According to the present invention, a sealant for liquid crystalsexcellent in strong adhesion strength and low liquid crystalcontamination has been enabled to be obtained. Moreover, production ofliquid crystal display cell excellent in reliability has been enabled tobe attained by using the sealant for liquid crystals of the presentinvention in a liquid crystal dropping method.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in detail below.

The sealant for liquid crystals of the present invention ischaracterized by containing (a) a radiation curable resin represented bythe general formula (1), (b) a photopolymerization initiator and (c) aninorganic filler having an average particle diameter of 3 μm or less asessential components.

In the radiation curable resin (a) represented by the general formula(1), R¹ represents a hydrogen atom or a methyl group, and preferably itis a hydrogen atom. R² represents a hydrogen atom, a halogen atom, ahydroxyl group, a linear, branch or cyclic monovalent alkyl group having1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms,and preferably it is a hydrogen atom. R³ represents a hydrogen atom or amethyl group, and preferably it is a hydrogen atom. The number mrepresents an integer of 1 to 4, and m may be the same or different. Thenumber n of the repeating units is a positive number in the range of 0to 20, and preferably it is a positive number in the range of 0 to 1.5.

In the radiation curable resin (a) represented by the general formula(1), particularly preferred in the present invention is a radiationcurable resin represented by the general formula (2), and p is apositive number in the range of 0 to 20, and preferably it is a positivenumber in the range of 0 to 1.5.

The radiation curable resin (a) used in the present invention can beobtained by subjecting resorcin diglycidyl ether, catechol diglycidylether, hydroquinone diglycidyl ether, etc. to esterification reactionwith a (meta)acrylic acid in an amount equivalent to the epoxy group.This synthetic reaction can be performed by a commonly known method. Forexample, an equivalent amount of (meta)acrylic acid is added to resorcindiglycidyl ether together with a catalyst (for example,benzylmethylamine, triethylamine, benzyltrimethylammonium chloride,triphenylphosphine, triphenylstibine, etc.) and a polymerizationinhibitor (for example, methoquinone, hydroquinone, methylhydroquinone,phenothiazine, dibutylhydroxytoluene, etc.), and esterification reactionis performed for example at 80 to 110° C. The thus obtained(meta)acrylated resorcin diglycidyl ether is a resin which has aradically polymerizable (meta)acryloyl group.

In addition, the radiation curable resin (a) used in the presentinvention can be obtained by reacting resorcin, catechol, hydroquinone,etc., with glycidyl (meta)acrylate which is equivalent or excessive tothe OH-group thereof. This synthetic reaction can be performed by acommonly known method. For example, glycidyl (meta)acrylate equivalentto the OH-group of resorcin is added to the resorcin together with acatalyst (for example, benzylmetlhylamine, triethylamine,benzyltrimethylammonium chloride, triphenylphosphine, triphenylstibine,etc.) and a polymerization inhibitor (for example, methoquinone,hydroquinone, methylhydroquinone, phenothiazine, dibutylhydroxytoluene,etc.), and esterification reaction is performed at 80 to 110° C. Thethus obtained (meta)acrylated resorcin diglycidyl ether is a resin whichhas a radically polymerizable (meta)acryloyl group.

Furthermore in the present invention, the content ratio of the radiationcurable resin (a) to the sealant for liquid crystals is usually about30% by weight to 80% by weight, preferably about 40% by weight to about75% by weight to the weight of the whole sealant for liquid crystals.Moreover, the viscosity of radiation curable resin (a) is preferablyabout 30 to about 500 Pa·S.

As an photopolymerization initiator (b) used in the present invention,any kind of photopolymerization initiator such as a radical typeinitiator and a cation type initiator may be used, but it is preferablya radical type initiator from a viewpoint of liquid crystalcontaminating properties. The radical initiator includesbenzylmethylketal, 1-hydroxycyclohexyl phenyl ketone,diethylthioxanthone, benzophenone, 2-ethyl anthraquinone, 2-hydroxy2-methylpropiophenone,2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane,2,4,6-trimethylbenzoyldiphenylphosphine oxide etc., for example, and aninitiator having a sensitivity near i line (365 nm) whose influence onthe characteristics of liquid crystal is relatively small and a lowliquid crystal contaminating properties is preferable. Specific examplesof such an initiator include carbazole initiators such as3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole.

In the sealant for liquid crystals of the present invention, thecompounding ratio of the photopolymerization initiator (b) to theingredient (a) is preferably 0.01 to 5 weight parts to 100 weight partsof the ingredient (a), particularly preferably 0.1 to 3 weight parts. Ifthe photopolymerization initiator is less than 0.1 weight parts,photo-curing reaction is not sufficient, and if it increases more than 3weight parts, there is too much quantity of the initiator andcontamination by the initiator on the liquid crystal and deteriorationof the curable resin properties may be caused.

Examples of the inorganic filler (c) used in the present inventioninclude fused silica, crystal silica, silicon carbide, silicon nitride,boron nitride, calcium carbonate, magnesium carbonate, barium sulfate,calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconiumdioxide, aluminum hydroxide, magnesium hydroxide, calcium silicate,aluminum silicate, lithium aluminum silicate, zirconium silicate, bariumtitanate, glass fiber, carbon fiber, molybdenum disulfide, asbestos,etc., preferably it is fused silica, crystal silica, silicon nitride,boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica,talc, clay, alumina, aluminum hydroxide, calcium silicate, and aluminumsilicate, and more preferably it is fused silica, crystal silica,alumina and talc. Two or more of these inorganic fillers may be mixedand used.

The average particle diameter of the inorganic filler used in thepresent invention is not more than 3 μm, and the minimum is on the orderof 0.003 μm. If the average particle diameter is larger than 3 μm, gapcannot be suitably formed when the top and the bottom glass substratesare stuck together in the production of a liquid crystal cell. Theaverage particle diameter of the inorganic filler was measured with alaser diffraction and dispersion type particle diameter distributionmeasuring instrument (dry type) (product of SEISHIN, Inc. Company;LMS-30).

The content ratio in the sealant for liquid crystals of the inorganicfiller used in the present invention is usually 5 to 40% by weight,preferably 15 to 25% by weight. Since the adhesion strength to the glasssubstrate decreases and wetproof reliability is also deteriorated whenthe content ratio of the inorganic filler is lower than 5% by weight,the adhesion strength after moisture absorption also tends to greatlydecrease. When the content ratio of the inorganic filler is more than40% by weight, the filler content is so much that the sealing is hard tobe deformed, and there is a case where gap in the liquid crystal cellcannot be formed.

The sealant for liquid crystals of the present invention preferablycontains an epoxy resin (d) in addition to the above-mentioned threeessential components (a) to (c). The epoxy resin (d) used in the presentinvention is not limited, but an epoxy resin which does not elute intothe liquid crystals in an amount of 0.5% by weight or more based on theepoxy resin when the epoxy resin is brought directly into contact withthe liquid crystals whose amount is 10 times of the epoxy resin and isallowed to stand at 120° C. for 1 hour is preferable from the viewpointof liquid crystal contaminating properties. Examples of such an epoxyresin include bisphenol S type epoxy resin represented by the formula(3):

resorcin diglycidyl ether polymer represented by the formula (4):

wherein x represents an integer of 1 to 10;diglycidyl ether of the ethylene oxide addition bisphenol S representedby the formula (5):

and diglycidyl ether of ethylene oxide addition bisphenol fluorenerepresented by the formula (6):

but it is not limited to these.

The quantification of the eluted substances can be conducted by gaschromatography using pentadecane as an internal standard.

The amount of hydrolyzed chlorine of the epoxy resin used in the presentinvention is preferably 600 ppm or less, and more preferably 300 ppm orless. If the amount of hydrolyzed chlorine increases more than 600 ppm,contaminating properties of the sealant for liquid crystals to liquidcrystal may become a problem. The amount of hydrolyzed chlorine can bequantified by dissolving about 0.5 g of epoxy resin in 20 ml of dioxaneand refluxing with 1N KOH/5 ml ethanol solution for 30 minutes, andtitrating with 0.01N silver nitrate.

The content ratio of the epoxy resin (d) in the sealant for liquidcrystals is usually about 1% by weight to about 40% by weight,preferably about 5% by weight to about 30% by weight to the wholesealant for liquid crystals.

The sealant for liquid crystals of the present invention preferablycontains a heat-curing agent (e). Although the heat-curing agent is notparticularly limited as long as it reacts with an epoxy resin (d) toform a cured product, it is important that the reaction starts promptlyand uniformly when heated without contaminating the liquid crystal witha sealant for liquid crystals and there is little change in viscosity atthe time of use at room temperature. In order to hold the deteriorationof the properties of the sealed liquid crystal as little as possible,low-temperature curing ability of generally 120° C. for about 1 hour isrequired as heat curing conditions in the case of liquid crystaldropping method. It is particularly preferable in view of the abovepoints to use multifunctional hydrazides and polyhydric phenols as aheat-curing ingredient in the sealant for liquid crystals of the presentinvention.

The multifunctional dihydrazides as used herein mean a dihydrazideshaving two or more hydrazide groups in a molecule and specific examplesthereof include carbohydrazide, oxalic dihydrazide, malonic dihydrazide,succinic dihydrazide, adipic dihydrazide, adipic dihydrazide, pimelicdihydrazide, suberic dihydrazide, azelaic dihydrazide, sebacicdihydrazide, dodecanediodihydrazide, hexadecanediohydrazide, maleicdihydrazide, fumaric dihydrazide, diglycollic dihydrazide, tartaricdihydrazide, malic dihydrazide, isophthalic dihydrazide, terephthalicdihydrazide, 2,6-naphthoic dihydrazide, 4,4-bis-benzene dihydrazide,1,4-naphthoic dihydrazide, 2,6- pyridine dihydrazide, 1,2,4-benzenetrihydrazide, pyromellitic tetrahydrazide, 1,4,5,8-naphthoictetrahydrazide, and dihydrazides having a valine hydantoin skeleton suchas 1,3-bis(hydrazinocarbonoethyl)-5-isopropyl hydantoin, but it is notlimited to these. In the case of using a multifunctional dihydrazide asa curing agent, it is preferable to make the particle diameter fine sothat the particles disperse uniformly in order to use it as a latentcuring agent. Among the multifunctional dihydrazides, dihydrazides arepreferable, and particularly preferred are isophthalic dihydrazide anddihydrazides having valine hydantoin skeletons from a viewpoint ofliquid crystal contaminating properties.

On the other hand, polyhydric phenols mean phenols having two or morehydroxyl groups in a molecule and specific examples thereof includebisphenol A, bisphenol F, bisphenol S, bisphenol E, phenol novolac,cresol novolac, trisphenol methane type novolac, biphenyl type novolac,naphthalene type novolac, etc., but it is not limited to these.

If the average particle diameter of the ingredient (e) is too large,there causes problems such as malfunction that gap cannot be suitablyformed when the top and the bottom glass substrates are stuck togetherin the production of a liquid crystal cell with a narrow gap, andtherefore the average particle diameter of the ingredient (e) ispreferably 3 μm or less and more preferably 2 μm or less. Similarly, themaximum particle diameter is preferably 8 μm or less, and morepreferably 5 μm or less. The particle diameter of a curing agent wasmeasured with a laser diffraction and dispersion type particle diameterdistribution measuring instrument (dry type) (product of SEISHIN, Inc.Company; LMS-30). It is preferable to perform production so that theaverage particle diameter may not be extremely small (for example, below0.1 μm).

In the sealant for liquid crystals of the present invention, thecompounding ratio of the ingredient (e) is preferably 0.8 to 1.5equivalent and more preferably 0.9 to 1.2 equivalent to the amount ofthe epoxy group of the ingredient (d). If the amount of the ingredient(d) is less than 0.8 equivalent, heat-curing reaction is insufficient,and adhesive strength and glass transition temperature may become low.On the other hand, if the amount is more than 1.5 equivalent, the curingagent may remain, adhesive strength may decrease and the pot life may bedeteriorated.

The sealant for liquid crystals of the present invention preferablycontains a silane coupling agent (f) in order to raise adhesionstrength. Examples of the silane coupling agent include silane couplingagents such as 3-glycidoxypropyltrimethoxysilane,3-glycidoxypropylmethyldimethoxysilane,3-glycidoxypropylmethyldimethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane,N-(2-aminoethyl)3-aminopropyl methyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane,vinyltrimethoxysilane,N-(2-(vinylbenzylamino)ethyl)3-aminopropyltrimethoxysilanehydrochloride, 3-methacryloxypropyltrimethoxysilane,3-chloropropylmethyldimethoxysilane and 3-chloropropyltrimethoxysilane.Two or more of these silane coupling agents may be mixed and used. Amongthese, the silane coupling agent in which the silane coupling agent hasan amino group is preferable in order to obtain more good adhesionstrength. By using a silane coupling agent, adhesion strength improvesand the sealant for liquid crystals excellent in wetproof reliability isobtained.

The content ratio of the sealant for liquid crystals of the silanecoupling agent (f) is usually about 0.01% by weight to about 5% byweight, preferably about 0.02% by weight to about 1% by weight to thetotal weight of the liquid crystal.

Additives such as an organic solvent, organic fillers, pigments,leveling agents, and defoaming agents can be further compounded in asealant for liquid crystals of the present invention if needed.

In order to obtain the sealant for liquid crystals of the presentinvention, for example, first the ingredient (a), the ingredient (b),and the ingredient (d) and if needed further the ingredient (f) aredissolved and mixed. Subsequently, predetermined amounts of theingredient (e) as a heat-curing agent, the ingredient (c) and, ifneeded, a defoaming agent, a leveling agent, an organic filler, etc. areadded to this mixture, and the sealant for liquid crystals of thepresent invention can be produced by mixing uniformly with a well-knownmixing equipment, for example, three-rolls, sand mill, ball mill, etc.

The liquid crystal display cell of the present invention comprises apair of substrates oppositely positioned at a predetermined interval onwhich predetermined electrodes are formed and the circumference of whichis sealed with a sealant for liquid crystals of the present invention,and liquid crystal is enclosed within the space. The kind of liquidcrystal enclosed is not particularly limited. Here, the substratesconsist of a combination at least one of which has light permeabilityand comprises glass, quartz, plastics, silicon, etc. As the productionprocess, for example, a spacer (gap control material) such as glassfiber is added on the sealant for liquid crystals and the sealant forliquid crystals is applied on one of the pair of substrates with adispenser etc., and the liquid crystal is dropped inside this sealantfor liquid crystals, another glass substrate is laid thereon in vacuum,and a gap is formed. After gap formation, ultraviolet ray is irradiatedon the sealed parts of the liquid crystal with an ultraviolet-rayirradiation equipment, and photo-curing is carried out. The amount ofultraviolet-rays irradiation is preferably 500 mJ/cm² to 6000 mJ/cm²,more preferably 1000 mJ/cm² to 4000 mJ/cm². Then, the liquid crystaldisplay cell of the present invention can be obtained by curing at 90 to130° C. for 1 to 2 hours. The thus obtained liquid crystal display cellof the present invention has no display defect resulted from liquidcrystal contamination and is excellent in adhesiveness and wetproofreliability. Examples of the spacer include glass fiber, silica bead,polymer bead, etc. Although the diameters differ according to thepurpose, it is usually 2 to 8 μm, preferably 4 to 7 μm. The amount usedis usually 0.1 to 4 weight parts, preferably 0.5 to 2 weight parts andmore preferably 0.9 to 1.5 weight parts to 100 weight parts of thesealant for liquid crystals of the present invention.

EXAMPLES

The present invention is described in more detail below by way ofexamples.

Synthesis Example 1 Synthesis of epoxy acrylate of resorcin diglycidylether(epoxy acrylate A)

Resorcin diglycidyl ether resin was dissolved in toluene,dibutylhydroxytoluene was added thereto as a polymerization inhibitor,and the temperature was elevated to 60° C. Then, acrylic acid in anamount of 100% equivalent of the epoxy group was added, the temperaturewas further elevated to 80° C., trimethylammonium chloride which was areaction catalyst was added thereto, and the mixture was stirred at 98°C. for about 50 hours. The obtained reaction liquid was washed withwater, toluene was evaporated and the object epoxy acrylate of resorcinwas obtained (Epoxy acrylate A).

Synthesis Example 2 Synthesis of epoxy acrylate of bisphenol F epoxy(epoxy acrylate B)

Bisphenol F epoxy resin (product of Nippon Kayaku Co., Ltd., RE-404P,epoxy equivalent: 160 g/eq, hydrolyzed amount: 30 ppm) was dissolved intoluene, dibutylhydroxytoluene was added thereto as a polymerizationinhibitor, and the temperature was elevated to 60° C. Then, acrylic acidin an amount of 100% equivalent of the epoxy group was added, thetemperature was further elevated to 80° C., trimethylammonium chloridewhich was a reaction catalyst was added thereto, and the mixture wasstirred at 98° C. for about 50 hours. The obtained reaction liquid waswashed with water, toluene was evaporated and the object epoxy acrylateof bisphenol F epoxy was obtained (Epoxy acrylate B).

Synthesis Example 3 Synthesis of 60% partial epoxy acrylate of bisphenolF epoxy (epoxy acrylate C)

Bisphenol F epoxy resin (product of Nippon Kayaku Co., Ltd., RE-404P,epoxy equivalent: 160 g/eq, hydrolyzed amount: 30 ppm) was dissolved intoluene, dibutylhydroxytoluene was added thereto as a polymerizationinhibitor, and the temperature was elevated to 60° C. Then, acrylic acidin an amount of 60% equivalent of the epoxy group was added, thetemperature was further elevated to 80° C., trimethylammonium chloridewhich was a reaction catalyst was added thereto, and the mixture wasstirred at 98° C. for about 50 hours. The obtained reaction liquid waswashed with water, toluene was evaporated and the object partial epoxyacrylate of bisphenol F epoxy was obtained (Epoxy acrylate C).

Experiment Example 1 Liquid Crystal Contaminating Properties Test (Onlyby Heat)

0.1 g each of epoxy acrylates A to C synthesized above was put into asample tube, respectively, and a liquid crystal (product of Merck,MLC-6866-100) was added to allow the acrylate to contact directly, andthe mixture was placed in a 120° C. oven for 1 hour, and after that itwas left at room temperature for 0.5 hour. After only the liquid crystalwas taken out, quantification of the ingredients which eluted to thisliquid crystal was carried out by gas chromatography with pentadecaneused as an internal standard. The quantity of eluted substances wasshown by % by weight to liquid crystal in Table 1. Although tile epoxyacrylate of resorcin diglycidyl ether (epoxy acrylate A) is low inviscosity, elution was about ⅓ as compared with 100% epoxy acrylate ofbisphenol F epoxy (epoxy acrylate B). Three types of eluted substancesof the epoxy resin from 60% partial epoxy acrylate substance ofbisphenol F epoxy (epoxy acrylate C), one in which the epoxy group ofboth ends were acrylated, a monoacrylated compound in which only oneside was acrylated, and the starting materials were confirmed. Thus,elution of the epoxy acrylates of resorcin diglycidyl ether (epoxyacrylate A) is smaller than that of the other epoxy acrylates.

TABLE 1 Epoxy Epoxy Epoxy Acrylate A Acrylate B Acrylate C Viscosity 50Pa · s 150 Pa · s 80 Pa · s Quantification of Eluted 0.11% 0.37% 1.0%Substances (GC-MS)

Example 1

A resin liquid was obtained by heating and dissolving 80 weight parts ofthe epoxy acrylate A of Synthetic Example 1, 20 weight parts of EBPS-300(product of Nippon Kayaku Co., Ltd., epoxy equivalent: 233 g/eq,bisphenol S type epoxy resin) as an epoxy resin, 1.8 weight parts of3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole (product ofAsahi Denka Kogyo, Adeka Optomer N-1414) as a radical generating typephotopolymerization initiator, 1.2 weight parts of an aminosilanecoupling agent (N-β(aminoethyl)γ-aminopropyltrimethoxysilane, product ofShin-etsu Silicone, KBM-603) at 90° C. After the mixture was allowed tocool to room temperature, 5 weight parts of isophthalic dihydrazide(product name: IDH-S; jet mill pulverized grade by Otsuka Chemistry Inc.further finely pulverized with a jet mill; melting point: 224° C.,active hydrogen equivalent: 48.5 g/eq; average particle diameter: 1.7μm; maximum particle diameter: 7 μm), 30 weight parts of alumina(product of C.I. Kasei, Inc., SPC-aluminum, average particle diameter:1.0 μm) and 7 weight parts of core shell rubber particles: paraloidEXL-2655 (product of Kureha Chemical Industry Co., Ltd., core layer:cross-linked polybutadiene, shell layer: alkyl methacrylate-styrenecopolymer, average particle diameter: 200 nm) were added and blendedwith 3 rolls and the sealant for liquid crystals of the presentinvention was obtained. The viscosity (25° C.) of the sealant for liquidcrystals was 250 Pa·s (R-type viscometer (product of Toki Sangyo Co.,Ltd.)).

Example 2

A resin liquid was obtained by heating and dissolving 80 weight parts ofthe epoxy acrylate A of Synthesis Example 1, 20 weight parts of EBPS-300(product of Nippon Kayaku Co., Ltd., epoxy equivalent: 233 g/eq,bisphenol S type epoxy resin) as an epoxy resin, 1.8 weight parts of3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole (product ofAsahi Denka Kogyo, Adeka Optomer N-1414) as a radical generating typephotopolymerization initiator, 1.2 weight parts of an aminosilanecoupling agent (N-β(aminoethyl)γ-aminopropyltrimethoxysilane, product ofShin-etsu Silicone, KBM-603) at 90° C. After the mixture was allowed tocool to room temperature, 6.5 weight parts ofAmicure-VDH(1,3-bis(hydrazinocarbonoethyl)-5-isopropyl hydantoin;product of Ajinomoto Fine Techno finely pulverized with a jet mill), 30weight parts of alumina (product of C.I. Kasei, Inc., SPC-Al, averageparticle diameter: 1.0 μm) and 7 weight parts of core shell rubberparticles: paraloid EXL-2655 (product of Kureha Chemical Industry Co.,Ltd., core layer: cross-linked polybutadiene, shell layer: alkylmethlacrylate-styrene copolymer, average particle diameter: 200 nm) wereadded and blended with 3 rolls and the sealant for liquid crystals ofthe present invention was obtained. The viscosity (25° C.) of thesealant for liquid crystals was 350 Pa·s (R-type viscometer (product ofToki Sangyo Co., Ltd.)).

Comparative Example 1

A resin liquid was obtained by heating and dissolving 70 weight parts ofthe epoxy acrylate B of Synthesis Example 2, 20 weight parts of EBPS-300(product of Nippon Kayaku Co., Ltd., epoxy equivalent: 233 g/eq,bisphenol S epoxy resin) as an epoxy resin, 10 weight parts of reactionproduct of dipentaerythritol caprolactone and acrylic acid (product ofNippon Kayaku Co., Ltd., DPCA-60, hexafunctional) as a reactive dilutingagent, 1.8 weight parts of3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole (product ofAsahi Denka Kogyo, Adeka Optomer N-1414) as a radical generating typephotopolymerization initiator, 1.2 weight parts of an aminosilanecoupling agent (N-β(aminoethyl)γ-aminopropyltrimethoxysilane, product ofShin-etsu Silicone, KBM-603) at 90° C. After the mixture was allowed tocool to room temperature, 5 weight parts of isophthalic dihydrazide(product name: IDH-S; jet mill pulverized grade by Otsuka Chemistry Inc.further finely pulverized with a jet mill; melting point: 224° C.,active hydrogen equivalent: 48.5 g/eq; average particle diameter: 1.7μm; maximum particle diameter: 7 μm), 30 weight parts of alumina(product of C.I. Kasei, Inc., SPC-Al, average particle diameter: 1.0 μm)and 7 weight parts of core shell rubber particles: paraloid EXL-2655(product of Kureha Chemical Industry Co., Ltd., core layer: cross-linkedpolybutadiene, shell layer: alkyl methacrylate-styrene copolymer,average particle diameter: 200 nm) were added and blended with 3 rollsand the sealant for liquid crystals of the present invention wasobtained. The viscosity (25° C.) of the sealant for liquid crystals was400 Pa·s (R-type viscometer (product of Toki Sangyo Co., Ltd.)).

Comparative Example 2

A resin liquid was obtained by heating and dissolving 100 weight partsof the epoxy acrylate C of Synthesis Example 3, 1.8 weight parts of3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole (product ofAsahi Denka Kogyo, Adeka Optomer N-1414) as a radical generating typephotopolymerization initiator, 1.2 weight parts of an aminosilanecoupling agent (N-β(aminoethyl)γ-aminopropyltrimethoxysilane, product ofShin-etsu Silicone, KBM-603) at 90° C. After the mixture was allowed tocool to room temperature, 5 weight parts of isophthalic dihydrazide(product name: IDH-S; jet mill pulverized grade by Otsuka Chemistry Inc.further finely pulverized with a jet mill; melting point: 224° C.,active hydrogen equivalent: 48.5 g/eq; average particle diameter: 1.7μm; maximum particle diameter: 7 μm), 30 weight parts of alumina(product of C.I. Kasei, Inc., SPC-Al, average particle diameter: 1.0 μm)and 7 weight parts of core shell rubber particles: paraloid EXL-2655(product of Kureha Chemical Industry Co., Ltd., core layer: cross-linkedpolybutadiene, shell layer: alkyl methacrylate-styrene copolymer,average particle diameter: 200 nm) were added and blended with 3 rollsand the sealant for liquid crystals of the present invention wasobtained. The viscosity (25° C.) of the sealant for liquid crystals was200 Pa·s (R-type viscometer (product of Toki Sangyo Co., Ltd.)).

Experiment Example 2

Next, liquid crystal contaminating properties test (UV+heat), adhesionstrength test and glass transition temperature measurement wereconducted on the sealant for liquid crystals of Examples 1 and 2, andComparative Examples 1 and 2.

Liquid Crystal Contaminating Properties Test (by UV+Heat)

The following measurement of the specific resistance in contacted liquidcrystal was performed as an index of liquid crystal contaminatingproperties.

Into a sample tube, 0.1 g each of the sealants for liquid crystal wasput, respectively, and 1 ml of a liquid crystal (product of Merck,MLC-6866-100) was added. After the mixture was irradiated withultraviolet ray of 2000 mJ/cm² with UV irradiation equipment, it wasplaced in a 120° C. oven for 1 hour, and after that it was left at roomtemperature for 0.5 hour. After only the liquid crystal was taken outfrom the treated sample tubes, quantification of the ingredients whicheluted to this liquid crystal was carried out by gas chromatography withpentadecane used as an internal standard. The results are shown in Table2.

Adhesion Strength Test

As a spacer, 1 g of glass fiber (5 μm) was added to 100 g of theobtained sealant for liquid crystals, and the mixture was mixed andstirred. This sealant for liquid crystals is applied on a glasssubstrate of 50 mm×50 mm, and a piece of glass of 1.5 mm×1.5 mm wasstuck on the sealant for liquid crystals, irradiated with ultravioletray of 2000 mJ/cm² with UV irradiation equipment, and then placed in a120° C. oven for 1 hour to effect curing. The sheer strength of thepiece of glass was measured. The results are shown in Table 2.

Glass Transition Temperature

The obtained sealant for liquid crystals sandwiched between polyethyleneterephthalate (PET) films so that the sealant was made into a thin filmhaving a thickness of 100 μm was irradiated with ultraviolet ray of 2000mJ/cm² with UV irradiation equipment, and then placed in a 120° C. ovenfor 1 hour to effect curing. After the curing, PET films were removedand the cured sealant was used as a sample. The glass transitiontemperature was measured with TMA test machine (product of Shinku-RikoInc.) in a tension mode. The results are shown in Table 2.

According to Table 2, good numerical values are similarly obtained inboth Examples and Comparative Examples as for physical propertiesrequired for sealants such as adhesion strength and glass transitiontemperature. However, eluted substances to liquid crystal are much lessin the sealants for liquid crystal of Examples 1 and 2 as compared withthe sealants for liquid crystal of Comparative Examples 1 and 2.Therefore, it can be said that the sealants for liquid crystal ofExamples 1 and 2 are sealants for liquid crystal which are veryexcellent in reliability of liquid crystal contaminating properties ascompared with the sealants for liquid crystal of Comparative Examples 1and 2.

TABLE 2 Comparative Comparative Example 1 Example 2 Example 1 Example 2Viscosity (Pa · s) 250 350 400 200 Adhesion strength (MPa) 70 75 75 75Glass Transition Temperature (° C.) 100 100 90 85 Liquid crystalcontaminating test (120° C. × 1 hr.) Quantification of eluted substances(ppm) Epoxy Acrylate A 200 150 Epoxy Acrylate B 800 Epoxy Acrylate C6500 Bis S type epoxy 250 200 250 Total 450 350 1050 6500 Liquid crystalcontaminating test (UV2J + 120° C. × 1 hr.) Quantification of elutedsubstances (ppm) Epoxy Acrylate A 100 80 Epoxy Acrylate B 480 EpoxyAcrylate C 1500 Bis S type epoxy 100 80 100 Total 200 160 580 1500

1. A sealant for liquid crystals comprising as essential ingredients (a)a radiation curable resin represented by the general formula (2):

wherein the number p of the repeating units is a positive number in therange of 0 to 20, which is obtained by subjecting resorcin diglycidylether to acrylic acid in an amount equivalent to the number of epoxygroups in the molecule of diglycidyl ether; (b) a radicalphotopolymerization initiator; and (c) an inorganic filler having anaverage particle diameter of 3 μm or less; and further comprising (d) anepoxy resin and (e) a heat-curing agent, wherein the epoxy resin (d) isan epoxy resin which does not elute into the liquid crystals in anamount of 0.05% by weight on the liquid crystals when the epoxy resin isbrought directly into contact with the liquid crystals whose amounts is10 times of the epoxy resin and is allowed to stand at 120° C. for 1hour.
 2. The sealant for liquid crystals according to claim 1, whereinthe radiation curable resin (a) has a content of 30% by weight to 80% byweight based on the total amount of the sealant for liquid crystals. 3.The sealant for liquid crystals according to claims 1, wherein theradiation curable resin (a) has a viscosity of 30 to 500 Pa·s.
 4. Thesealant for liquid crystals according to claim 1 wherein the radicaltype photopolymerization initiator (b) is a carbazole initiator.
 5. Thesealant for liquid crystals according to claim 1, wherein theheat-curing agent (e) is a dihydrazide.
 6. The sealant for liquidcrystals according to claim 5, wherein the dihydrazide is a dihydrazidehaving a skeleton of isophthalic dihydrazide and/or valine hydantoin. 7.The sealant for liquid crystals according to claim 1, wherein theheat-curing agent (e) is a polyhydric phenol.
 8. The sealant for liquidcrystals according to claim 1, further comprising (f) a silane couplingagent.
 9. The sealant for liquid crystals according to claim 8, whereinthe silane coupling agent is a silane coupling agent having an aminogroup.
 10. A liquid crystal display cell which is sealed with a curedproduct of a sealant for liquid crystals according to claim
 1. 11. Aprocess for producing a liquid crystal display cell comprising droppingliquid crystals inside a sealant for liquid crystals according to claim1 formed on a substrate and attaching another substrate thereto.